TY  - JOUR
A1  - Wolter, Steffen
A1  - Aizezers, Janis
A1  - Fennel, Franziska
A1  - Seidel, Marcus
A1  - Würthner, Frank
A1  - Kühn, Oliver
A1  - Lochbrunner, Stefan
T1  - Size-dependent exciton dynamics in one-dimensional perylene bisimide aggregates
JF  - New Journal of Physics
N2  - The size-dependent exciton dynamics of one-dimensional aggregates of substituted perylene bisimides are studied by ultrafast transient absorption spectroscopy and kinetic Monte-Carlo simulations as a function of the excitation density and the temperature in the range of 25-90 degrees C. For low temperatures, the aggregates can be treated as infinite chains and the dynamics is dominated by diffusion-driven exciton-exciton annihilation. With increasing temperature the aggregates dissociate into small fragments consisting of very few monomers. This scenario is also supported by the time-dependent anisotropy deduced from polarization-dependent experiments.
KW  - rotational diffusion
KW  - spectroscopy
KW  - dyes
KW  - annihilation
KW  - migration
KW  - films
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-135190
VL  - 14
IS  - 105027
ER  - 
TY  - JOUR
A1  - Wiessner, M.
A1  - Rodriguez Lastra, N. S.
A1  - Ziroff, J.
A1  - Forster, F.
A1  - Puschnig, P.
A1  - Dössel, L.
A1  - Müllen, K.
A1  - Schöll, A.
A1  - Reinert, F.
T1  - Different views on the electronic structure of nanoscale graphene: aromatic molecule versus quantum dot
JF  - New Journal of Physics
N2  - Graphene's peculiar electronic band structure makes it of interest for new electronic and spintronic approaches. However, potential applications suffer from quantization effects when the spatial extension reaches the nanoscale. We show by photoelectron spectroscopy on nanoscaled model systems (disc-shaped, planar polyacenes) that the two-dimensional band structure is transformed into discrete states which follow the momentum dependence of the graphene Bloch states. Based on a simple model of quantum wells, we show how the band structure of graphene emerges from localized states, and we compare this result with ab initio calculations which describe the orbital structure.
KW  - well
KW  - confinement
KW  - states
KW  - Ag(111)
KW  - photoemission
KW  - vicinal surfaces
KW  - coronene
KW  - energy
KW  - films
KW  - nanographenes
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130184
VL  - 14
IS  - 113008
ER  -